4age Very Low comp on cyl 3 and 4

[AE092]

Hi Julz,

It sounds like you had a very similar issue to me I had about 8 months back. While cruising home one day, the car started to suddenly sound like a lawnmower/wrx. I didn't know what the issue was until she was towed home and had a mobile mechanic come 'round for a look. He performed a compression test and confirmed it was a Blown Head Gasket (BHG) between cylinders 2 and 3, right in the middle. I had the engine rectified with a rebuilt head, TODA 0.8mm head gasket, big port camshafts, new Trust timing belt, GMB water pump and strengthened head bolts from Japan. I'm near certain the stock head gasket is 1.0mm so 0.8mm is a good/minor upgrade with the mild cams.

If you need a shop that is knowledgeable with engine heads then I've got a contact for you. Also, my mechanic did alot of the labour work in regards to removing/fitting the head and ancillaries so if you need a contact for that then I can help you out. Pm if you like

cheers

[oldcorollas]

1mm before being compressed, or 1mm after being torqued down?

[AE092]

good question, I'd say 1mm before being compressed

[trdee]

ive heard otherwise, 1.1mm

if i can be bothered i would fish out that spare head gasket i have laying around, but its fucking cold and it doesnt really matter anyway.

[oldcorollas]

hmmm silver top = 1.15-1.2 http://www.toymods.org.au/forums/sho...-gasket-VS-TRD

i sit corrected

but 7A gasket is something like 0.6mm? and two layer MLS

[Julz01]

will try source a 0.8 or so head gasket

gotten a bit further with it today and have taken off the intake manifold.

just wondering if its worth keeping the TVIS system. currently on the manifold at the moment but is it worth just deleting it all together.

also any hints on taking the head off. obviously there the 4 bolts in the valley but are the more under the cams?

[oldcorollas]

all the bolts are under the cam covers... (somone else can confirm you can pull th ehead without taking off the cams)
are the ones you are seeing in the valley the "freeze plugs" ? (the allen key plugs in the following picture)
http://www.ae92gts.com/gze/images/gze_rebuild/head1.jpg

here you can see where the bolts go from the bottom. 2 on either side, between each cylinder, and at each end = 10 bolts

[Julz01]

yea they are the ones I have mistaken for head bolts. guess this got a whole lot more fun.

anything I should watch out for when taking the cams out?

[oldcorollas]

you may not need to take out the cams... if you can get to the head bolts from above with them in place.

[andrew_mx83]

yeah 10 head bolts under the cam covers, you will need a 3/8" drive MULTIHEX 10mm socket to get em out. cant remember if the cams need to come out, you may get away with rotating them out the way of the tool if they foul a couple of the bolts.

[Julz01]

had a look just now and looks like almost all of them should be ok to remove without having to take the cam out except for the front bolt which has the distributor drive cog on the cam in the way.

also should I remove them with a certain torque spec or is it just when tightening them up that I should torque them correctly

thanks

[oldcorollas]

i think it's better to remove them in stages. not specificall y atorque (as you are loosening, not tightening) but 2-3 steps perhaps?

[andrew_mx83]

yeah do it over a few steps, crack all the bolts 1/2 turn first then undo them over another couple of passes paying attention to the valves that are held open. cams are easy to bend/snap if the valve spring pressure pushing against the lobe is unsupported.

basically i ease up the bolts on the lobes that are holding valves open a couple of turns, then spin the others out to about the same amount, few more turns on the offending lobe then loosen the others etc til there is no more pressure on the cam.

ive had too much to drink to explain it properly....

[andrew_mx83]

heres the sequence toyota recommend for the 7m

removal: http://www.cygnusx1.net/Supra/Librar...aspx?S=EM&P=41
installation: http://www.cygnusx1.net/Supra/Librar...aspx?S=EM&P=53

i ASSUME these are the sequences for the cam at TDC.



being a 4cyl the 4age should be the same just simpler

[oldcorollas]

he's removing head.. in which case, this page is relevant
http://www.cygnusx1.net/Supra/Librar...aspx?S=EM&P=39